Many photosynthetic organisms exhibit light-dependent regulation of growth and development, including photoregulation of pigmentation, physiology, and form. We recently demonstrated that the photoregulation of cellular and filament morphology in Fremyella diplosiphon is under control of a photosensory photoreceptor and differentially impacted by photosynthetic pigment accumulation. Biliprotein photoreceptor RcaE controls the light-dependent regulation of pigmentation and of cell and filament morphology in F. diplosiphon, primarily in response to green and red light as a part of a light acclimation process known as complementary chromatic adaptation (CCA). Our recent investigations into the regulation of CCA underscored the largely independent regulation of pigmentation and cell shape by RcaE. However, recent studies on the regulation of phycobiliprotein biosynthesis indicated that filament length may depend upon correct photoregulation of photosynthetic pigment levels. Taken together, these studies suggest that aspects of the regulation of morphology in F. diplosiphon are independent of the regulation of pigmentation, yet other features of morphology depend upon the accurate photoregulation of pigment levels.
Keywords: cellular morphology; complementary chromatic adaptation; cyanobacteria; photomorphogenesis; photoregulation; phycobiliprotein.